The System Unit

Slides By Rana Usman SattarStudent Of BBA(Hons)PMAS Arid Agriculture University RawalpindiGmail: ranaa.usman@gmail.comFacebook: usman.shan86@yahoo.com

The System UnitThe system unit is a case that contains electroniccomponents of the computer used to process data. System units are available in a variety of shapes and sizes. The case of the system unit, sometimes called the chassis, is made of metal or plastic and protects the internal electronic components from damage. All computers and mobile devices have a system Unit.

The MotherboardThe motherboard, sometimes called a

systemboard, is the main circuit board of the system

unit. Many electronic components attach to theMotherboard, others are built into it.

Processor

The processor, also called the central processing unit (CPU), interprets and carries out the basic instructions that operate a computer.

The processor significantly impacts overall computing power and manages most of a computer’s operations.

Most processor chip manufacturers now offer multi-core processors. A processor core, or simply core, contains the circuitry necessary to execute instructions.

Processors contain a control unit and an arithmetic logic unit (ALU).

These two components work together to perform processing operations.

The Control UnitThe control unit is the component ofthe processor that directs and coordinatesmost of the operations in the computer. it interprets each instruction issued bya program and then initiates the appropriateaction to carry out the instruction. Types of internal components that the

controlunit directs include the arithmetic/logic unit , registers, and buses.

The Arithmetic Logic UnitThe arithmetic logic unit (ALU), another

component of the processor, performs arithmetic, comparison, and Other operations. Arithmetic operations include basic calculations such

as addition, subtraction, multiplication, and division. Comparison operations involve comparing one dataitem with another to determine whether the first item is greater than, equal to, or less than the other item.

Machine CycleFor every instruction, a processor repeats aset of four basic operations, which comprisea machine cycle (1) fetching(2) Decoding (3) executing(4) storing

• Fetching is the process of obtaining a program instruction or data item from memory.

• Decoding refers to the process of translating the instruction into signals the computer can execute.

• Executing is the process of carrying out the commands.

• Storing, in this context, means writing the result

to memory (not to a storage medium).

RegistersA processor contains small, high-speed storagelocations, called registers, that temporarily

holddata and instructions. Registers are part of the processor, not part of memory or a permanent storage device. Processors have many different types of registers, each with a specific storage function.

The System ClockThe processor relies on a small quartz crystalcircuit called the system clock to control thetiming of all computer operations.the system clock generates regular electronic pulses, or ticks, that set the operating pace of components of the system unit.Each tick equates to a clock cycle The pace of

the system clock, called the clock speed, is

measured by the number of ticks per second

• Heat sinks/• pipes and liquid cooling technologies often

are• used to help dissipate processor heat.• A heat sink is a small ceramic or metal

component• with fins on its surface that absorbs and• disperses heat produced by electrical

components• such as a processor

Processor CoolingHeat sinkspipes and liquid cooling technologies often

are used to help dissipate processor heat.A heat sink is a small ceramic or metal

component with fins on its surface that absorbs and disperses heat produced by electrical components such as a processor .

Heat Sinker

Parallel ProcessingParallel processing is a method that uses

multiple processors simultaneously to execute a single program or task .

Parallel Processing

Memory• Memory consists of electronic

componentsthat store instructions waiting to be executed.• Memory stores three basic categories of items 1-: the operating system and other• system software that control or maintain the

computer and its devices .2-:application programsthat carry out a specific task such asword processing . 3-:The data being processedby the application programs and resultinginformation.

Memory Sizes

1 Kilobyte = 1,024 1 Megabyte =1,048,576 1 Gigabyte =1,073,741,8241 Terabyte =1,099,511,627,776

Types of Memoryvolatile memoryNonvolatile memory

Types of MemoryRAM (random access memory), also

called main memory, consists of memory chips that can be read from and written to by the processor and other devices.

Types of MemoryTWO basic types of RAM 1-: Dynamic RAM 2-:Static RAM

memory modulesThere are three types of memory modules.1-:SIMMs(single inline memory module)2-:DIMMs(dual inline memory module)3-:RIMMs(Rambus inlinememory module)

MEMORY MODULES

Types of MemoryCache Memory Cache Memory helps

speed the processes of the computer because it stores frequently used instructions and data.

types of memory cacheL1 cacheL2 cache

types of memory cache• L1 cache L1 cache usually has a very

small capacity ranging from 8 KB to 128 KB. The more

common sizes for personal computers are32 KB or 64 KB.• L2 cache L2 cache is slightly slower than

L1 cache but has a much larger capacity, ranging from 64 KB to 16 MB.

Types of MemoryROM(Read only memory) ROM is

nonvolatile, which means its contents are not lost when power

is removed from the computer. In addition tocomputers, many devices contain ROM chips.For example, ROM chips in printers containdata for fonts.

TYPES OF ROMThere are two types of ROM1-:PROM2-:EEPROM

TYPES OF ROM• PROM (programmable read-only memory) A PROM chip is a blank ROM chip on

which a programmer can write permanently. Programmers use microcode instructions to program a PROM

chip. Once a programmer writes the microcodeon the PROM chip, it functions like aregular ROM chip and cannot be erased orchanged.

TYPES OF ROMEEPROM (electrically erasable

programmable read-only memory) EEPROM chip, allows

a programmer to erase the microcode with an electric signal.

Types of MemoryFlash Memory Flash memory is a

type of nonvolatile memory that can be erased electronically and rewritten, similar to EEPROM.

Types of Memory• CMOS(complementary metal-oxide semiconductor) (CMOS pronounced SEE-moss) technology because it provides high

speeds and consumes little power.

CMOS technology uses battery power to retain information even when the power to the computer is off.

Battery-backed CMOS memory chips, for example, can keep the calendar, date, and time current even when the computer is off.

The flash memory chips that store a computer’s startup information often use CMOS technology.

Memory Access TimesAccess time is the amount of time it takesthe processor to read data, instructions, andinformation from memory. A computer’s access time directly affects

how fast the computer processes data.

Expansion Slots and Adapter Cards• Expansion Slots An expansion slot is

a socket on the motherboard that can hold an adapter card.

• Adapter Cards An adapter card, sometimes

called an expansion card, is a circuit board that enhances functions of a component of the system unit and/or provides connections to peripherals.

ADAPTER CARD

Removable Flash MemoryA type of memory which can easily insert

and remove from a slot of a personal computer.

A memory card is a removable flash memory device, usually no bigger than 1.5" in height or

width, that you insert and remove from a slotin a personal computer, game console,

mobiledevice, or card reader/writer.

Removable Flash Memory

Ports and Connectors• PORTS A port is the point at which a peripheral

attachesto or communicates with a system unit so that theperipheral can send data to or receive informationfrom the computer. • CONNECTORSA connector joins a cable to a port. A connectorat one end of a cable attaches to a port on the

system unit, and a connector at the other end ofthe cable attaches to a port on the peripheral.

Ports and Connectors

Ports and Connectors• USB Ports A USB port, short for

universal serial bus port, can connect up to 127 different peripherals together with a single connector. Devices that connect to a USB port include the following:

mouse, printer, digital camera, scanner, speakers,

portable media player, optical disc drive, smartphone, PDA, game console, and removablehard disk.

Ports and ConnectorsFireWire Ports FireWire port is

similar to a USB port in that it can connect multiple types of devices that require faster data transmission speeds such as digital video cameras, digital VCRs,

color printers, scanners, digital cameras, andDVD drives, to a single connector.

Ports and ConnectorsBluetooth Port Bluetooth technology

uses radio waves to transmit data between two

devices.A Bluetooth wireless port adapter that will

convert an existing USB port into a Bluetooth port .

BLUETOOTH DEVICE

Ports and ConnectorsSCSI Port A special high-speed parallel

port called a SCSI port, allows you to attach SCSI(pronounced skuzzy) peripherals such as disk drives and printers.

Ports and Connectors• eSATA Port• An eSATA port, or external SATA

port, allows you to connect an external SATA (Serial Advanced Technology Attachment) hard disk to a computer.

SATA hard disks are popular because of their fast data transmission speeds.

• eSATA connections provide up to six times faster data transmission speeds than external hard disks attached to a computer’s USB or FireWire port .

Ports and ConnectorsIrDA Port IrDA port is used infrared

signals to transmit data one device to another device. Devices that use IrDA ports include a smart phone, PDA, keyboard, mouse, and printer. Several of these devices use a high-speed IrDA port, sometimes called a fast infrared port.

IrDA ports

Ports and Connectors• Serial Ports A serial port is a type of

interface that connects a device to the system unit by transmitting data one bit at a time.

• MIDI Port A special type of serial port thatconnects the system unit to a musical

instrument , such as an electronic keyboard, is called a MIDI port.

Port Replicators and Docking StationsPort Replicators A port replicator is an external devicethat provides connections to peripherals

through ports built into the device. The mobile user accesses peripherals by connecting the port replicator to a USB port or a special port on the mobile computer.

Port Replicators and Docking StationsDocking Stations A docking station, which is an

externaldevice that attaches to a mobile computer or

device, contains a power connection and provides connections to peripherals; it usually also includes slots for memory cards, optical disc drives, and other devices

Docking Stations

BusesBuses are used to transfer bits from input devices to memory, from memory to the

processor, from the processor to memory, and from memory to output or storage devices.

BUSES

PARTS OF BUSES• There are two parts of buses• DATA BUS• ADDRESS BUS1-:Data Bus The data bus is used to

transfer actual data.2-:Address Bus• The address bus is used to

transfer information about where the data should reside in

memory.

TYPES OF BUSES• There three types of buses• System Bus• Backside Bus• Expansion Bus1-:System Bus• A system bus, also called

thefront side bus ( FSB), is part of the

motherboardand connects the processor to main memory.

TYPES OF BUSES2-:Backside Bus A backside bus ( BSB) connects

the processor to cache.3-:Expansion Bus An expansion bus allows the

processor to communicate with peripherals.

BaysA bay is an opening inside thesystem unit in which you can install

additionalequipment. A bay is different from a slot on

themotherboard, which is used for the

installationof adapter cards. A drive bay is a

rectangularopening that typically holds disk drives.

TYPES OF Bays• External Bays• Internal Bays1-:External Bays An external bay allows a

user to access openings in the bay from outside the system unit.

2-:Internal Bays An internal bay is concealed

entirely within the system unit. Hard disk drives are installed in internal bays.

BAYS